1. Calvary Health Care Sydney
KNEE PAIN
Updated May 2013

2. Outline Knee pain and common causes Differential diagnosis
Baker’s Cyst
Osgood-Schlatter Lesion
ACL & PCL
Examination
Investigations

3. Knee Pain
Knee pain is a common presenting complaint with many possible causes.
Teenage girls and young women: more likely to have patellar tracking problems such as patellar subluxation and patellofemoral pain syndrome.
Teenage boys and young men: more likely to have knee extensor mechanism problems such as tibial apophysitis (Osgood-Schlatter lesion) and patellar tendonitis.
Older adults: Osteoarthritis of the knee joint is common.
Referred pain resulting from hip joint pathology, such as slipped capital femoral epiphysis, also may cause knee pain.
Active patients: more likely to have acute ligamentous sprains and overuse injuries such as pes anserine bursitis and medial plica syndrome.
Trauma: may result in acute ligamentous rupture or fracture, leading to acute knee joint swelling and hemarthrosis. Septic arthritis may develop in patients of any age, but crystal-induced inflammatory arthropathy is more likely in adults.

4. Common Causes of Knee Pain by Age Group
Children and Adolescents
Adults
Older Adults
Patellar subluxation
Patellofemoral pain syndrome (chondromalacia patellae)
Osteoarthritis
Tibial apophysitis (Osgood-Schlatter lesion)
Medial plica syndrome 
Crystal-induced inflammatory arthropathy: gout, pseudogout
Jumper's knee (patellar tendonitis)
Pes anserine bursitis
Popliteal cyst (Baker's cyst)
Referred pain: slipped capital femoral epiphysis
Trauma: ligamentous sprains (anterior cruciate, medial collateral, lateral collateral), meniscal tear
Osteochondritis dissecans
Inflammatory arthropathy: rheumatoid arthritis, Reiter's syndrome
Septic arthritis

5. Causes of Acute Knee Pain
Common
Less Common
Not to be missed
Medial Meniscus Tear
Patellar tendon rupture
Fracture of the Tibial Plateau
MCL Sprain
Acute Patellofemoral Joint Injury
Avulsion fracture
ACL rupture
Coronary Ligament Sprain
Osteochondritis Dissecans
Lateral Meniscus Tear
Bursal hematoma / bursitis
Reflex Sympathetic Dystrophy (post injury)
Articular Cartilage Injury
Acute fat pad impingement
PCL Sprain
Low Quadriceps Haematoma
Patellar Dislocation
Avulsion of Biceps Femoris Tendon
Dislocated Superior Tibiofibular Joint

6. Surrounding Musculature
Muscles surrounding the knee joint further contribute to knee stabilization during lower extremity movements
Primary muscles include the quadriceps anteriorly, hamstrings posteriorly, gluteus medius and tensor fascia lata/IT band laterally and the hip adductors medially
The repetitive, eccentric nature of muscular activity about the knee during sports may lead to fatigue related injuries

7. Differential Diagnosis of Knee Pain by Anatomic Site
Anterior Knee Pain
Posterior Knee Pain
Patellar subluxation or dislocation
Popliteal cyst (Baker's cyst)
Tibial apophysitis (Osgood-Schlatter lesion)
Posterior cruciate ligament injury
Jumper's knee (patellar tendonitis)
Patellofemoral pain syndrome (chondromalacia patellae)

8. Differential Diagnosis of Knee Pain by Anatomic Site
Medial Knee Pain
Lateral Knee Pain
Medial collateral ligament sprain
Lateral collateral ligament sprain
Medial meniscal tear
Lateral meniscal tear
Pes anserine bursitis
Iliotibial band tendonitis
Medial plica syndrome

9. The Relationship of Swelling to Diagnosis
Immediate
Delayed
No Swelling
0-2 Hours (hemarthrosis)
ACL rupture
Patellar Dislocation
6-24 hours (effusion)
Meniscus
MCL Sprain
The degree and time of onset of welling is an important diagnostic clue

10. Baker's Cyst

11. Baker’s Cyst Definition: A Chronic Knee Joint effusion
A Baker cyst, also called a popliteal cyst, is a synovial cyst located posterior to the medial femoral condyle between the tendons of the medial head of the gastrocnemius and semimembranosus muscles. It results from the abnormal collection of fluid inside the gastrocnemio-semimembranosus bursa.
A Baker cyst is lined by a true synovium, as it is an extension of the knee joint.
Popliteal cysts range from 1-40 cm3 (median 3 cm3).

12. Symptoms of Baker’s Cyst
Frequency
Popliteal Mass or Swelling
29/38
76%
Aching
12/38
32%
Knee Effusion
Thrombophlebitis
5/38
13%
Clicking of the knee
4/38
11%
Buckling of the knee
Locking of the knee
1/38 3%
There may be limitation in range of motion caused by pain or by the size of the cyst.

13. Popliteal Mass The most common presenting complaint or symptom
It is usually visible as a bulge behind the knee, which is particularly noticeable on standing and comparing to the opposite uninvolved knee. They are generally soft and minimally tender
Baker cysts can become complicated by protrusion of fluid down the leg between the muscles of the calf (dissection). The cyst can rupture, leaking fluid down the medial leg to sometimes give the medial ankle the appearance of a painless bruise. Baker cyst dissection and rupture are frequently associated with swelling of the leg and can mimic phlebitis of the leg

14. Phlebitis in the Leg
Inflammation of a vein, leading to the formation of a thrombus in the vein
Will cause the leg to swell with oedema fluid and feel stiff and painful
Significant number of patients (13%) have symptoms simulating deep venous thrombosis (DVT), a syndrome termed pseudothrombophlebitis
Therefore, exclude DVT in patients with popliteal cyst and leg swelling
A blood clot may be dangerous and requires immediate medical attention.

15. Medical Conditions Associated with Popliteal Cysts
Medical conditions associated with popliteal cysts, in descending order of frequency, are as follows:
Arthritides: Osteoarthritis, RA, Juvenile RA, Gout, Reiter syndrome, psoriasis & systemic lupus erythematosus.
Internal derangement: meniscal tears, ACL tears, osteochondral fractures
Infection: septic arthritis, tuberculosis
Chronic dialysis
Hemophilia
Hypothyroidism
Pigmented villonodular synovitis
Sarcoidosis
· In younger athletes a torn meniscus may be the underlying cause.
· Herniation of the knee joint capsule out into the back of the knee, which is more common in adults. This type of Baker's cyst is commonly associated with a tear in the meniscal cartilage of the knee.
· In older adults, osteoarthritis might be suspected as a possible cause.
Any damage within the knee joint may cause swelling and therefore a Baker's Cyst.
Patient Populations Prevalence, %
RA 5-58, Osteoarthritis 42, Internal derangements 5-18

16. Baker’s Cyst & Arthritis
Arthritis is the most common condition associated with Baker cyst. Of the arthritides, osteoarthritis is probably the most common cause of popliteal cyst. Although prevalence of Baker cyst in patients with inflammatory arthritis is higher than in patients with osteoarthritis, osteoarthritis is much more common than inflammatory arthritis.
Fam et al demonstrated that the occurrence of Baker cysts relates directly to the presence of knee effusion and severity of osteoarthritis.
In 99 consecutive patients with RA, Andonopoulos et al demonstrated Baker cysts on US in 47 patients (48%). Twenty patients (20%) had bilateral cysts. Of 198 patients' knees, 67 (34%) had popliteal cysts, yet only 29 cysts (43%) were diagnosed clinically.

17. Diagnosis of a Baker’s Cyst
Arthrography (a type of x-ray examination that uses a contrast agent to image an anatomical joint): 5-46%
Ultrasound: 40-42%
Arthoscopy: 37%
Cadaveric dissections 30%
MRI 5-18%
Any damage within the knee joint may cause swelling and therefore a Baker's Cyst.
X-rays will not show the cyst or a meniscal tear but will show other abnormalities that may be present including arthritis.
MRI can be helpful to visualize the cyst and to demonstrate any meniscal injury.

18. Treatment of Baker’s Cyst
Often no treatment is necessary and the practitioner can observe the cyst over time. If the cyst is painful, treatment is usually aimed at correcting the underlying problem, such as arthritis or a meniscus tear.
Baker cysts often resolve with removal of excess knee fluid in conjunction with cortisone injection.
Medications are sometimes given to relieve pain and inflammation.
When cartilage tears or other internal knee problems are associated, surgery can be the best treatment option. During a surgical operation the surgeon can remove the synovium that leads to the cyst formation.
Baker's cysts usually disappear spontaneously, but the time in which they do so is variable.
Removal of the cyst is generally not done because it may damage nearby blood vessels and nerves.
  swollen tissue = synovium

19. Patellofemoral Pain Syndrome (Chondromalacia patellae)
Patellofemoral Syndrome is the term used to describe pain in and around the patella
Functional Anatomy
Full extension: Patella sits lateral to the trochlea
During Flexion: Patella moves medial and comes to lie within the intercondylar notch until 130º, when it starts to move lateral again.
Patella excursion is controlled by the quadriceps, particularly VMO & VL
With increasing knee flexion, a greater area of patellar articular surface comes into contact with the femur, therefore offsetting the increased load that comes with flexion

20. Patellofemoral Pain Syndrome Cont.
Loaded knee flexion activities subject the patellofemoral joint to loads many times the body weight.
Anatomically, the lateral structures of the PFJ are much stronger than the medial structures, so any imbalance in the forces will cause the patella to drift laterally.
Activity
Force through PFJ
Level Walking
0.5 x body weight
Going up stairs
3-4 x body weight
Squat
7-8 x body weight

21. Predisposing Factors Factors Cause Abnormal Biomechanics
Excessive Pronation
Femoral anteversion (internal femoral torsion)
High small patella (patella alta)
Increased Q angle
Soft tissue tightness
Muscles: Gastroc, H’strings, Rec Fem & ITB
Lateral Structures: Lateral retinaculum, ITB & VL
Muscle Dysfunction
VMO
Hip abductors / External rotators (glut med)
Training
Distance running
Hills, stairs
Q angle = angle between line of pull of Quads and line of patellar tendon
Femoral anteversion often referred to as ‘squinting patella’ and is associated with an increased lateral force on the patella due to an increase in the valgus force that occurs during knee extension. Internal femoral torsion, in association with internal tibial rotation, can be secondary to excessive subtalar pronation. Internal femoral rotation can also occur in conjunction with external tibial rotation.
Hip internal rotation can be limited by soft tissue restriction, such as tight anterior joint capsule and/or short adductors, TFL, ilipsoas and rec fem. All of these restrict movement in the knee and hip therefore predisposing to patellofemoral pain.
Tightness in ITB results in overactivity in the TFL and diminished activity in the posterior fibres of glut med. The muscle imbalance persists because acting from a shortened position (that usually cross 2 joints) are readily recruited and strong, whereas muscles acting form an elongated position (usually postural muscles) are difficult to recruit and weak. A subject with a short ITB demonstrates excessive medial rotation of the hip during the stance phase of gait which means that the pelvis on the opposite side drops (trendelenberg sign). This hip movement will increase the dynamic Q angle and hence increase the potential for patellofemoral pain.
Soft tissue tightness is particularly prevalent during the adolescent growth spurt. The resultant inflexibility alters stress through the PFJ and also compromises muscle control as the muscles attempt to control a much longer lever.
Lateral structures are particularly tight, with the superficial structures (VL & ITB) restricting medial glide and the deep structures (lateral retinaculum) restricting medial tilt.
H’string an gastroc tightness cause a lateral tracking of the patella by increasing the dynamic Q angle.
When an individual with tight hamstrings runs, knee flexion increases with foot strike. Because the knee cannot strighten easily, ankle dorsiflexion must increase for the body to pass over the planted foot. If the talocrural joint is already maximally dorsiflexed, the foot will pronate, particularly at the subtalar joint. This increases the valgus vector force at the knee & hence increases the dynamic Q angle.
Therefore altered foot biomechanics, as a secondary as well as a primary problem, can alter tibial rotation and affect patellofemoral joint mechanics.

22. Tibial Apophysitis (Osgood-Schlatter Lesion)
The typical patient is a 13- or 14-year-old boy (or a 10- or 11-year-old girl) who has recently gone through a growth spurt.
Aggravated by:
Squatting
Walking up / down stairs
Forceful contraction of the quadriceps
Exacerbated by jumping and hurdling, because repetitive hard landings place excessive stress on the insertion of the patellar tendon.
A teenage boy who presents with anterior knee pain localized to the tibial tuberosity is likely to have tibial apophysitis, or Osgood-Schlatter lesion3,4 (Figure 1).5 The typical patient is a 13- or 14-year-old boy (or a 10- or 11-year-old girl) who has recently gone through a growth spurt.
The patient with tibial apophysitis generally reports waxing and waning of knee pain for a period of months. The pain worsens with squatting, walking up or down stairs, or forceful contractions of the quadriceps muscle. This overuse apophysitis is exacerbated by jumping and hurdling, because repetitive hard landings place excessive stress on the insertion of the patellar tendon.
On physical examination, the tibial tuberosity is tender and swollen, and may feel warm. The knee pain is reproduced with resisted active extension or passive hyperflexion of the knee. No effusion is present. Radiographs are usually negative; rarely, they show avulsion of the apophysis at the tibial tuberosity. However, the physician must not mistake the normal appearance of the tibial apophysis for an avulsion fracture.

23. Anterior & Posterior Cruciate Ligaments
Two important intra-articular ligaments that provide static support to the knee are the anterior (ACL) and posterior (PCL) cruciate ligaments.  The PCL and ACL are intra-articular but extrasynovial
The ACL originates from the medial and anterior aspect of the tibial plateau and runs superiorly, laterally, and posteriorly toward its insertion on the lateral femoral condyle
The ACL is composed of the anteriomedial and posteriolateral bundles. Together, these bundles provide approximately 85% of total restraining force of anterior displacement of the tibia on the femur
To a lesser degree, the ACL checks extension and hyperextension. Together with the posterior cruciate ligament (PCL), It also prevents excessive tibial medial and lateral rotation, as well as varus and valgus stresses
The ligaments are tense in all positions, but increase their tension in the extremes of flexion and extension
The PCL is the major stabilizer of the knee. It provides most of the restraint against posterior tibial displacement on the femur during flexion. The posterior fibers of the PCL prevent hyperextension. During flexion, the anterior fibers tighten and help prevent hyperflexion. The PCL resists internal tibial rotation during flexion by winding around the anterior cruciate ligament (ACL).
In terminal knee extension, the PCL and ACL, with the guidance of the menisci, help externally rotate the tibia to its correct position in relation to the femur (screw home mechanism).
The meniscofemoral ligaments (MFL) are associated intimately with the PCL. Their function is to pull the posterior horn of the lateral meniscus anterior and medial during flexion, balancing the action of the popliteus muscle, which, in addition to the MFL, attaches to the posterior horn of the lateral meniscus. The MFL also may function as a secondary restraint to posterior tibial translation after complete rupture of the PCL
The PCL is twice as strong as the ACL. It contains a larger cross-sectional area and possesses a higher tensile strength, explaining its lower rate of injury. The PCL fibers are oriented more vertically than the more oblique fibers of the ACL.

24. Anterior Cruciate Ligament
The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. Each year, approximately 100,000 people sustain ACL injuries with basketball, soccer, skiing, and gymnastics being the sports with the highest incidence
ACL injury rates are estimated to be two to eight times higher in females than males participating in the same sports
Numerous studies exploring why females are at a higher risk cite both intrinsic and extrinsic differences between genders

25. Anatomy and Biomechanics
Smaller notch width index. A smaller notch width index has been found to predispose females to ACL injuries. The smaller notch likely causes a shearing effect on the ACL by the femur. Although this smaller, A-shaped notch has been shown to be related to ACL injuries, there is no evidence that the relationship is causal
Increased ligamentous laxity. Females in general have ligaments that are more lax than males, which increases the risk of ACL rupture. In addition, it has been suggested that within the first year after surgery when “ligamentization” of the tendon occurs, females undergo a different remodeling response than males
Increased Q angle. The female pelvis is wider than the male pelvis, which increases the Q angle of the knee. This leads to increase stresses at the knee, and causes other compensatory deviations in the surrounding joints. Other changes that occur include femoral anteversion, tibial external torsion, and subtalar pronation
The cause of increased female susceptibility to ACL injury is unclear, but is likely due to a multitude of complex variables. Research has suggested three main views: anatomical and biomechanical considerations, neuromuscular imbalances, and hormonal influences.

26. Neuromuscular Imbalances
Research has shown disparity among females and males in knee proprioception and neuromuscular control
Quadriceps dominance pattern. Females demonstrate strength imbalance between quadriceps and hamstrings. Female athletes tend to rely on their quadriceps and gastrocnemius and less on their hamstrings when compared to males. In addition, females exhibited a delayed firing pattern of the hamstrings
Landing strategies. Females use different strategies when running, landing, or jumping than males and tend to land with an increased valgus moment. This may cause significant differences between their dominant and non-dominant knee. However, both knees may potentially be at an increased risk for ACL rupture. The dominant knee works to limit gravitational forces, while the non-dominant knee may be too weak to withstand such forces

27. Hormonal Influences
Female hormones have been suggested as a possible risk factor for ACL rupture. It has been hypothesized that these hormones increase ligament laxity and decrease ligament strength during the weeks prior to and immediately following the menstrual cycle.
However, further research is needed to confirm or deny the role of female sex hormones in ACL injury.
Most research on this topic has several limiting factors, including the reliance on subject self-report of menstrual cycle phase or the confounding factor of oral contraceptives [ 10 ].

28. Mechanism of Injury
The ACL is usually torn as a result of a quick deceleration, hyperextension or rotational injury that usually does not involve contact with another individual. This injury often occurs following a sudden change of direction
When hit from the side, injuries to the ACL are often associated with medial meniscus and medial collateral ligament (MCL) tears, collectively known as the “unhappy triad.”
In adolescents, the ACL may avulse from the tibial spine instead of rupturing

29. Signs and Symptoms
An acute ACL rupture is characterized by pain, hemarthrosis, and instability. At the moment of injury, many people report hearing or feeling a popping sensation
Common impairments typically include immediate swelling (0-2 hours), decreased strength and range of motion, inability to weight-bear and poor balance and coordination
Considerable pain in the knee that does not go away within the first few hours after the injury
Patients are functionally limited in their ability to ambulate, negotiate stairs, and perform basic and instrumental ADLs. If not properly addressed, these impairments could become chronic conditions
A feeling of unsteadiness and a tendency for the knee to "give-way," or an inability to bear weight on the injured leg
An audible "pop" or the perception of something snapping or breaking at the moment of injury
A feeling of "fullness or tightness" in the knee

30. Examination Observation: Standing, walking & Supine
Active Movements: Flexion & Extension
Passive Movements: Flexion & Extension
Palpation: PFJ, MCL, LCL, Medial & Lateral Joint line,
& in prone (hamstring tendons, Bakers Cyst, Gastroc origins)
Special tests
Presence of Effusion
Stability tests: MCL, LCL
ACL: Lachmans test, Anterior drawer test & Pivot shift test
PCL: Posterior Sag, reverse Lachmans test & posterior drawer test
Flexion / Rotation (McMurrays test)
Patellar Apprehension Test
PFJ

31. Investigations: X-ray
The specific indications for x-ray following acute knee injury are:
High speed injuries (suspect a tibial plateau fracture
Children or adolescents (who may avulse a bony fragment instead of tearing of a cruciate ligament)
If there is clinical suspicion of loose bodies
If hemarthrosis is present
If surgery is indicated